The present invention is directed to a dental patient chair comprising an arrangement for adjusting the seat height, the inclination position of the seat and backrest, as well as the position of the seat and backrest in a longitudinal direction relative to the base of the chair.
In order to be able to position a patient ergonomically and treatment-suited, i.e., optimally adjusted both with respect to the attendant as well as with respect to the treatment to be undertaken, it is necessary to be able to adjust both the seat and backrest, that form the upper chair part of a patient chair, both in height as well as in longitudinal direction of the chair and, over and above this, in its inclined position relative to a vertical or horizontal reference plane. Various designs are known for this purpose.
German OS 29 38 330 discloses a parallelogram linkage arrangement which is provided for the height adjustment of a seat. Although a relatively great stroke can be achieved with such a parallelogram linkage arrangement, it is necessarily a disadvantage that additional means must be provided in order to achieve initially addressed longitudinal adjustability of the upper chair part. German OS 22 26 572 discloses an arrangement for longitudinal adjusting, which can be a straight-line mechanism having a hooked-out curve for simultaneously lifting an end of the chair part adjacent the foot or foot end of the chair.
A scissor arm structure having mirror-inverted scissor arms arranged in pairs or having one set guided in corresponding longitudinal guide elements for longitudinal adjustment of an upper chair part are also known. An example is disclosed in U.S. Pat. No. 4,533,106, whose disclosure is incorporated by reference and which was based on German Application 32 28 834.
Although these latter scissor arm designs have proven themselves extremely well and have advantages over the earlier-known embodiments of being more space saving, relatively narrow limits are also nonetheless placed on these designs. For example, limits are placed on a design with respect to the demand for little mechanical outlay given an improvement in the motion possibilities, particularly relating to the height adjustment and longitudinal adjustability of the seat.